The disclosure relates to centrifugal compressors. More particularly, the disclosure relates to diffuser restriction/control rings.
U.S. Pat. No. 3,362,625 to Endress, Jan. 9, 1968, discloses an axially shiftable diffuser restriction ring positioned to intervene radially between an impeller outlet and a diffuser inlet. In a high capacity operating condition the ring is in a relatively retracted position. To reduce capacity, the ring is shifted toward a relatively inserted position, progressively occluding/throttling communication from the impeller outlet to the diffuser inlet. Various other compressors have various configurations of axially shiftable diffuser restriction rings. A variety of actuators exist for such rings ranging from purely hydraulic or pneumatic (e.g., where the ring is effectively a piston) to mechanical linkages whose ultimate actuator may be hydraulic or pneumatic or may be a motor, electromagnetic actuator, or the like.